The second-tier reserve is a broad international solvency, also known as the second-tier reserve. International liquidity refers to the international circulating assets that can be directly controlled by a country to adjust the balance of payments and pay off international debts when necessary, including gold, foreign exchange reserves and reserve assets, and special drawing rights that can be obtained from the International Monetary Fund according to the prescribed limits. There are broad sense and narrow sense. The broad definition includes not only the narrow scope, but also the sum of other foreign exchange resources that can be used in a country's international exchanges. For example, the foreign exchange reserves borrowed by a government through signing a temporary financing agreement with an international financial institution or government, the short-term foreign exchange assets of its commercial banks, and the medium-and long-term foreign exchange assets owned by its officials or private individuals (mainly referring to medium-and long-term foreign investment). What is shown in the balance sheet is the whole content of the official settlement project. Generalized international reserves comprehensively reflect a country's external solvency. The broad sense of international solvency can be divided into the following levels: (1) the reserves borrowed by the government and the short-term foreign exchange assets of domestic commercial banks are important indicators to measure a country's short-term solvency; (2) medium and long-term foreign exchange assets owned by a government and short-term foreign exchange assets held by private or other non-metallic institutions, but it takes a long time to obtain these assets; (3) Other foreign exchange assets beyond the narrow sense and above. Compared with tier 1 reserve, the difference mainly lies in the different liquidity. Tier 1 reserve is an international reserve asset directly controlled by the government, which is convenient and quick to use. Secondary reserve assets are limited by ownership and time, and their liquidity is not as good as that of primary reserve assets. If the government wants to use the short-term foreign exchange assets of private commercial banks, it must go through certain procedures and formalities. The composition and application of primary and secondary reserves is an important part of international reserve management. Different forms of reserve assets have different liquidity. Demand deposits, cash, bills of exchange and other assets are highly liquid and can be used as first-line reserves. Assets such as gold, silver and bonds are relatively illiquid and can be used as second-line reserves. Maintaining more first-line reserves is conducive to daily international payments, but it is not appropriate to regard all reserves as first-line reserves because other factors have to be considered. In the use of foreign exchange reserve assets, we should systematically accumulate information and analyze the risks and benefits of long-,medium-and short-term financial assets and investment methods under the premise of following the three principles of safety, liquidity and profitability. According to the principle of investment diversification, all foreign exchange reserves can be divided into "first-line reserves" according to the needs of import payment and foreign debt repayment in different currencies in different periods in China. Except for short-term payment, the rest can be invested in short-term financial assets according to actual needs. The level of secondary reserves varies greatly among countries in the world. By the early 1990s, developed capitalist countries such as the United States, Western European countries and Japan were still the strongest secondary reserves.